Small Area Contacts for Solid State Light Sources
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing solid state light sources, particularly UV LEDs, face challenges in achieving efficient hole injection due to high ionization energy of acceptor impurities in group III nitride heterostructures, leading to low hole concentration and increased turn-on voltage.
Innovation Solution
The design incorporates a contact with a plurality of small area contacts extending partially through the p-type layer, with a characteristic lateral size equal to or smaller than the depletion region width, to enhance hole injection into the active region, reducing the barrier height and increasing the electric field for improved carrier injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional large area contacts are used, then the contact area is large, but the hole injection efficiency is low due to high ionization energy of acceptor impurities
Solution Approach 1:
The contact structure is segmented into multiple small area contacts (e.g., nanowire contacts) distributed across the semiconductor layer, rather than using a single large area contact. This segmentation increases the total effective contact area for hole injection while maintaining low turn-on voltage through distributed contact points
Solution Approach 2:
The small area contacts create localized regions of high hole concentration at the contact points, where the electric field is concentrated. This local quality enhancement allows efficient hole injection at specific locations without requiring the entire contact area to be highly effective
2Quantity of substance
If a dielectric layer is added to form a hole accumulation layer, then the hole concentration is increased, but the turn-on voltage substantially increases
Solution Approach 1:
The invention extracts the essential function of hole accumulation from the dielectric layer approach and implements it directly through small area metal contacts on the semiconductor layer. This eliminates the need for the dielectric layer while maintaining the hole accumulation effect through localized contact geometry
Solution Approach 2:
The small area metal contacts serve as intermediaries that directly create hole accumulation regions in the semiconductor layer without requiring an intervening dielectric layer. The metal-semiconductor interface itself acts as the mediator for hole accumulation and injection
3Productivity
If the characteristic lateral size of small area contacts is reduced to equal or smaller than depletion region width, then the hole injection efficiency is significantly improved, but the manufacturing precision requirements increase
Solution Approach 1:
The invention changes the critical parameter from contact area size to contact density and distribution. By optimizing the number, spacing, and size of multiple small contacts rather than relying on a single large contact, the system achieves high hole injection efficiency while relaxing the precision requirements for individual contact dimensions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly improves hole injection into the active region by at least three orders of magnitude, enhancing the efficiency of solid state light sources while maintaining a lower turn-on voltage.
Implementation Method 1
the plurality of small area contacts have a characteristic lateral size at an interface between the small area contact and the semiconductor layer equal to or smaller than a characteristic depletion region width for the plurality of small area contacts
Implementation Method 2
a high electron concentration in the top AlGaN layer causes carrier tunneling through the junction and reduces the lateral spreading resistance
Data Source
AI summary
A contact for solid state light sources is described. The solid state light source can include an active region, such as a light emitting multiple quantum well, and a semiconductor layer, such as a p-type layer, from which carriers (e.g., holes) enter the active region. A contact can be located adjacent to the semiconductor layer and include a plurality of small area contacts extending only partially through the semiconductor layer. The plurality of small area contacts can have a characteristic lateral size at an interface between the small area contact and the semiconductor layer equal to or smaller than a characteristic depletion region width for the plurality of small area contacts.